This invention is directed to an improved method of applying a chemical anchoring adhesive into a borehole. The chemical anchoring adhesive is provided in the form of a highly viscous, self-contained rope or slug having a first resin-containing part and a second curing agent-containing part joined along an interface. The slug is sized to the depth of the borehole and manually inserted into the borehole. The rope is cut to yield a slug of desired size before or after insertion into a borehole. The first part and second part have two different colors which mix to yield a third color when subjected to the turning force of a driving tool.
Chemical anchoring adhesives are known which are composed of two or more components that react together and cure when mixed. U.S. Pat. No. 5,730,557, issued to Skupian et al., discloses a mortar mixture capsule unit for chemical attachment of anchors in boreholes. The capsule houses a filler material, and a chemical binder system contained in smaller capsules within the filler material. The cartridge is inserted into a borehole, and a driving tool is used to insert an anchor. The driving tool imparts motion to the anchor, which ruptures both the housing capsule and the smaller capsules contained within it, causing the chemical binder system to interact and mix with the filler. The interaction and mixing causes reaction and curing of the binder system/filler mixture, thereby securing the anchor within the borehole. A similar adhesive is sold by Hilti AG under the trade name xe2x80x9cHVUxe2x80x9d.
U.S. Pat. No. 5,731,366, issued to Moench et al., discloses a chemical plugging compound based on a free-radically polymerizable resin and a free-radical initiator spatially separated therefrom. The spatial separation can be effected by encapsulating the initiator in glass, gelatin or cellulose capsules. The plugging compound is described as being self-supporting and storage stable.
These and other prior art chemical anchoring adhesives and methods have certain disadvantages. One disadvantage is that one or both components are fluid, and must be wrapped, encapsulated or otherwise enclosed in a package prior to use. Thus, it is often not easy to vary the amount of adhesive used in a borehole, or the size of the housing capsule, while at the job site. Put another way, oversized and undersized boreholes often receive the same amount of predetermined, pre-packaged adhesive as boreholes of standard size.
Another disadvantage is that fluid adhesives may flow or spill from the boreholes during use, particularly after the package is ruptured by the anchor being driven. This problem is especially acute when the borehole is upside down and vertical, but also exists when the borehole is horizontal, or at an angle between horizontal and upside down vertical. Even when the adhesive is not completely fluid, the shapes of the prior art cartridges are typically not self-retentive, i.e., the cartridges will fall from overhead boreholes.
Another disadvantage is that the two components, binder and filler, must be completely segregated prior to use, to prevent premature interaction and reaction. The encapsulation techniques used to accomplish this require some precision and expense. Also, there is no assurance that the smaller capsules used to contain the binder will remain evenly dispersed among the filler until the adhesive capsule is used. Uneven dispersion of the binder and filler can lead to uneven or inadequate adhesion of the anchor.
Cartridge adhesives are another type of prior art adhesive. Cartridge adhesives include two separate parts which are simultaneously injected into a borehole using a two-barrel caulking gun which brings the two parts together at the point of injection, whereupon they react upon entering the borehole. Disadvantages of cartridge adhesives and methods include excessive packaging waste, excessive adhesive waste due to unmixed, unused material remaining in the caulking barrels, and insufficient viscosity, which permits the material to run out of vertical overhead boreholes, and to sag in horizontal boreholes.
The present invention is directed to a method of applying a chemical anchoring adhesive to the interior of a borehole. The method includes the steps of providing a chemical anchoring adhesive in the form of a highly viscous, self-contained slug whose length is selected based on the depth of the borehole, inserting the slug into the borehole, providing an anchor pin, and driving the anchor pin into the borehole using a driving tool that imparts rotary motion to the pin. The adhesive slug includes a first part having a first color, and a second part having a second color different from the first. The first part includes a resin, and the second part includes a curing agent. The rotational motion of the anchor pin mixes the first and second parts together, resulting in formation of a substantially homogeneous mixture having a third color different from the first and second colors. The appearance of the third color, and disappearance of the first and second colors, indicates that the mixing is complete.
The adhesive composition may be produced in the form of a rope, which can be cut into slugs of the desired length either before the slugs are inserted into a borehole, or after a rope end is inserted into a borehole. The weight ratio of the first and second parts is substantially consistent along the entire length of the slug, to ensure formation of a substantially homogeneous cured composition upon mixing. Thus, the adhesive composition is both self-measuring and self-retaining due to its shape, viscosity and axial homogeneity.
With the foregoing in mind, it is a feature and advantage of the invention to provide a method of applying an anchoring adhesive into a borehole which yields a high strength bond and a substantially homogeneous cured composition.
It is also a feature and advantage of the invention to provide a method of applying an adhesive composition into a borehole which does not result in spilling of adhesive from overhead or horizontal boreholes, before or during mixing.
It is also a feature and advantage of the invention to provide a method for applying an adhesive composition into a borehole which includes the use of a color indicator to advise a worker when the mixing of the two adhesive parts is complete.
The foregoing and other features and advantages will become further apparent from the following detailed description of the presently preferred embodiments, read in conjunction with the accompanying drawings and examples. The detailed description, drawings and examples are illustrative rather than limiting, the scope of the invention being defined by the appended claims and equivalents thereof.